Introduction to Communication System: AM Radio Kit

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Introduction to Communication SystemAM Radio Kit

• ECE 002
• Dr. Ahmadi
• Department of Electrical and Computer Engineering
• The George Washington University

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Part I. Communication System and Amplitude
Modulation
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Communication System

• Communication systems send information
• electronically over communication channels
• Many different types of systems which convey
• many different types of information
• Design challenges include hardware, system, and
• network issues
• Communication systems recreate transmitted
• information at receiver with high fidelity

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Communication System

• Source encoder converts message into message
  signal or bits.
• Transmitter converts message signal or bits into
  format appropriate for channel transmission
  (analog/digital signal).
• Channel introduces distortion, noise, and
  interference.
• Receiver processes received signal back to
  message signal.
• Source decoder decodes message signal back into
  original message.

Source Encoder
Transmitter
Signal Channel
Receiver
Source Decoder
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Amplitude Modulation(AM)

• Modulation
• The process of converting a signal so that it can
  be successfully sent through a medium.
• The addition of the original signal to a carrier
  signal
• Types of Modulation
• Analog Modulation AM,FM, etc
• Digital Modulation
• History 1900s AM invented and popularized by De
  Forest commercial radio station begins
  broadcasting in Pittsburgh 1920.

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Amplitude Modulation(AM)

• AM works by varying the amplitude of the
  transmitted signal in relation to the information
  being sent. For example, changes in the signal
  amplitude can be used to reflect the sounds to be
  reproduced by a speaker
• Audio signal - fa
• Carrier signal - fc

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Part II. Introduction toReceiverAM-780 Radio
Kit
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Receiver AM Radio Kit

• Model AM-780
• A standard AM radio frequency receiver
• Radio frequency (RF) 3kHz 300GHz
• AM Broadcast Frequencies 535kHz 1605kHz

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(No Transcript)
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AM Radio 535kHz 1605kHz
FM Radio 88MHz 108MHz
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AM-780 Block Diagram
Antenna
LC Circuit
Transistor (IC 484)
Diodes
IC LM 386 Chip

• Component List
• Printed Circuit Board(PCB)
• (mechanically support and electrically connect
  electronic components)
• LC Circuit Inductors and Capacitors.
• (Selects the input signals by different
  frequencies)
• IC 484 Transistor.
• (Amplifies the selected input signal)
• Peak Detector Two diodes.
• (Detects the peak of the amplified input signal)
• IC LM-386 chip Power amplifier
• Specifications http//www.national.com/mpf/LM/LM3
  86.htmlOverview
• Antenna, Speaker, Resistors/Potentiometers and
  Wires

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Circuit Board

• Printed Circuit Board

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Resistors

• Use bands to tell resistors apart and to find
  value

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Capacitor

• An electronic component that has ability to store
  a charge and block DC current.

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Semiconductors
Diodes
Integrated Circuits IC 386
Transistor 484
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Other Parts
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Part III.Soldering
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Soldering Safety Precautions

• Never touch the element or tip of the soldering
  iron. They are very hot (about 400C) and will
  give you a nasty burn.
• Take great care to avoid touching the mains flex
  with the tip of the iron. The iron should have a
  heatproof flex for extra protection. An ordinary
  plastic flex will melt immediately if touched by
  a hot iron and there is a serious risk of burns
  and electric shock.
• Always return the soldering iron to its stand
  when not in use. Never put it down on your
  workbench, even for a moment!
• Work in a well-ventilated area. The smoke formed
  as you melt solder is mostly from the flux and
  quite irritating. Avoid breathing it by keeping
  you head to the side of, not above, your work.
• Wash your hands after using solder. Solder
  contains lead which is a poisonous metal.

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Preparing the soldering iron

• Place the soldering iron in its stand and plug
  in. The iron will take a few minutes to reach
  its operating temperature of about 400C.
• Dampen the sponge in the stand. The best way to
  do this is to lift it out the stand and hold it
  under a cold tap for a moment, then squeeze to
  remove excess water. It should be damp, not
  dripping wet.
• Wait a few minutes for the soldering iron to warm
  up. You can check if it is ready by trying to
  melt a little solder on the tip.
• Wipe the tip of the iron on the damp sponge.
  This will clean the tip.
• Melt a little solder on the tip of the iron.
  This is called 'tinning' and it will help the
  heat to flow from the iron's tip to the joint. It
  only needs to be done when you plug in the iron,
  and occasionally while soldering if you need to
  wipe the tip clean on the sponge.

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Preparing the soldering iron
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Start soldering

• Hold the soldering iron like a pen, near the base
  of the handle. Imagine you are going to write
  your name! Remember to never touch the hot
  element or tip.
• Touch the soldering iron onto the joint to be
  made. Make sure it touches both the component
  lead and the track. Hold the tip there for a few
  seconds and...
• Feed a little solder onto the joint. It should
  flow smoothly onto the lead and track to form a
  volcano shape as shown in the diagram. Apply the
  solder to the joint, not the iron.
• Remove the solder, then the iron, while keeping
  the joint still. Allow the joint a few seconds
  to cool before you move the circuit board.
• Inspect the joint closely. It should look shiny
  and have a 'volcano' shape. If not, you will need
  to reheat it and feed in a little more solder.
  This time ensure that both the lead and track are
  heated fully before applying solder.

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Start soldering
Resistor 1
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Start soldering
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Soldering Tips

• Ensure that items to be soldered are perfectly
  clean. This can be achieved with wire wood or
  fine emery cloth. Just because a piece of metal
  looks bright and clean it may not be.
• Make a good mechanical connection by wrapping
  wires around each other or around a terminal.
• When applying heat, do not apply it to the
  solder. Heat the base material, e.g. wires so
  they become sufficiently hot to melt the solder
  and flow it into the joint. A small amount of
  fresh solder on the tip when you begin soldering
  will help to carry heat from the iron to the
  joint.
• When solder has been applied to a joint smoothly
  slide the iron away to leave the joint neat.
• Avoid moving joint or wire after removing iron.
  Blowing on the joint will speed cooling.
• On electrical and electronic components avoid too
  much heat. A heat sink can be used to dissipate
  heat away from the component.
• Do not apply more solder than needed. Excess
  solder can cause short circuits.
• It is advisable to pre tin components before
  soldering, especially stranded wire. Twist the
  strands together, then heat and saturate with
  solder.
• Sweating a joint is easy after tinning. Just
  twist wires together and apply heat.
• To desolder a joint apply heat and use a
  soldering aid like solder wick to remove solder
  and separate joint. Be sure to use new solder
  when re-soldering.
• Fumes from some fluxes can be unpleasant so be
  sure there is good ventilation in the work area.
• Do not use a file to clean soldering tip, wiping
  on a wet sponge when tip is hot should keep tip
  clean.

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Soldering Tips
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Part IV.Assembling Your Radio Kit
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Schematic Diagram AM-780K
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Assemble Components to the PCB
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Assemble Components to the PCB
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Assemble Components to the PCB
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Assemble Components to the PCB
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Assemble Components to the PCB
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Install Battery Holder
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Install Antenna
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Alignment
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Lets Begin Working on Your Radio Kit